Constraint shape

A constraint
is a specification for conditions and propositions that must be maintained as true for the system to be valid. Constraints are expressed as text within braces ({ }) and may be written in a predefined language, such as Object Constraint Language (OCL) or in natural language.

Connect a constraint to one or more elements

Drag the control handle
at the center of the Constraint shape and glue it to a connection point
on another element.